Definition:
The refrain is a phrase, line, or lines repeated at intervals during a poem and especially at the end of a stanza. A device of great antiquity, it is found in the Egyptian Book of the Dead, the Bible, Greek, and Latin verse, Provençal and Renaissance verse, and in many ballads.
Example
One of the famous example of refrain is a lyric by Sir Thomas Wyatt:
Disdain me not without desert,
Nor leave me not so suddenly;
Since well ye wot that in my heart
I mean ye not but honestly.
Disdain me not.
Refuse me not without cause why,
Nor think me not to be unjust;
Since that by lot of fantasy
This careful knot needs knit I must.
Refuse me not.
Mistrust me not, though some there be
That fain would spot my steadfastness;
Believe them not, since that we see
The proof is not as they express.
Mistrust me not.
Forsake me not till I deserve
Nor hate me not till I offend;
Destroy me not till that I swerve;
But since ye know that I intend,
Forsake me not.
Disdain me not that am your own:
Refuse me not that am so true:
Mistrust me not till all be known:
Forsake me not ne for no new.
Disdain me not.
Also read; What is Pantomime; definition and features